//将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。 
//
// 
//
// 示例 1： 
// 
// 
//输入：l1 = [1,2,4], l2 = [1,3,4]
//输出：[1,1,2,3,4,4]
// 
//
// 示例 2： 
//
// 
//输入：l1 = [], l2 = []
//输出：[]
// 
//
// 示例 3： 
//
// 
//输入：l1 = [], l2 = [0]
//输出：[0]
// 
//
// 
//
// 提示： 
//
// 
// 两个链表的节点数目范围是 [0, 50] 
// -100 <= Node.val <= 100 
// l1 和 l2 均按 非递减顺序 排列 
// 
//
// Related Topics 递归 链表 👍 3029 👎 0


package leetcode.editor.cn;

// [21]合并两个有序链表

public class MergeTwoSortedLists_21 {
    public static void main(String[] args) {
        Solution solution = new MergeTwoSortedLists_21().new Solution();
    }
    //leetcode submit region begin(Prohibit modification and deletion)

    /**
     * Definition for singly-linked list.
     * public class ListNode {
     * int val;
     * ListNode next;
     * ListNode() {}
     * ListNode(int val) { this.val = val; }
     * ListNode(int val, ListNode next) { this.val = val; this.next = next; }
     * }
     */
    class Solution {
        public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
            ListNode cur1 = list1, cur2 = list2;

//            ListNode head = list1.val < list2.val ? list1 : list2;
            ListNode head = new ListNode();
            ListNode cur = head;
            while (cur1 != null && cur2 != null) {
                if (cur1.val < cur2.val) {
                    cur.next = cur1;
                    cur1 = cur1.next;
                } else {
                    cur.next = cur2;
                    cur2 = cur2.next;
                }
                cur = cur.next;
            }
            if (cur1 != null) {
                cur.next = cur1;
            }
            if (cur2 != null) {
                cur.next = cur2;
            }
            return head.next;
        }
    }

    //leetcode submit region end(Prohibit modification and deletion)
    private class ListNode {
        int val;
        ListNode next;

        ListNode() {
        }

        ListNode(int val) {
            this.val = val;
        }

        ListNode(int val, ListNode next) {
            this.val = val;
            this.next = next;
        }
    }
}

